Origin of the improved photo-catalytic activity of F-doped ZnWO4: A quantum mechanical study

Two different mechanisms for improving photo-catalytic activity in different types of F-doped ZnWO₄ are tentatively proposed, based on density function theory calculations. When the lattice O atom is substituted by one F atom, our calculations show that a reduced W⁵⁺ center adjacent to the doped F atom will act as a trap for the photo-induced electron, and will thus result in a reduction of electron-hole recombination and improvement of the photo-catalytic activity. For the interstitial F-doped model, partial F 2p states mixing with O 2p states localize above the top of the valence band and act as the frontier orbital level. Electronic transitions from these localized states induce a red shift of about 54 nm of the optical absorption edge. This work shows that F-doped ZnWO₄ will be a promising photo-catalyst with favorable photo-catalytic activity in the UV region.